Molded type heat insulating gasket

ABSTRACT

A heat insulating gasket structure with a molded body, and having bolt holes passing through raised bosses, is provided with a fluid passageway encircled by sealing members of packing material of a greater height than the raised bosses and having a plan area substantially less than that of the body. Sealing and heat insulation are accomplished by drawing mating flanges together to compress the sealing members to the height of the bosses and insulating air gaps result between the mating flanges and the molded body.

United States Patent Farnam MOLDED TYPE HEAT INSULATING GASKET Inventor:Robert G. Farnam, New Lisbon,

Wis.

[73] Assignee: F. D. Farnam Co., New Lisbon, Wis.

22 Filed: Jan. 21, 1974 21 Appl. No.: 434,871

[52] US. Cl. 277/166 [51] Int. Cl. Fl6j 15/10 [58] Field of Search277/166, 211, 235 B [56] References Cited UNITED STATES PATENTS3,191,950 6/1965 Hiltner 277/211 3,655,210 4/1972 Farnam et a]. 277/235B 3,889,961 [451 June 17, 1975 Primary Examiner-Robert I. SmithAttorney, Agent, or Firm-Mann, Brown, McWilliams & Bradway ABSTRACT Aheat insulating gasket structure with a molded body, and having boltholes passing through raised bosses, is provided with a fluid passagewayencircled by sealing members of packing material of a greater heightthan the raised bosses and having a plan area substantially less thanthat of the body. Sealing and 'heat insulation are accomplished bydrawing mating flanges together to compress the sealing members to theheight of the bosses and insulating air gaps result between the mat-'ing flanges and the molded body.

4 Claims, 3 Drawing Figures MOLDED TYPE HEAT INSULATING GASKETBACKGROUND OF THE INVENTION This invention pertains to insulatinggaskets, particularly those of the type that are used between acarburetor and the engine manifold.

There has been disclosed in Farnam et a]. US. Pat. No. 3,655,210 a heatinsulating gasket, which has been successfully used in automotiveengines between the carburetor body and the intake manifold, but, asengine temperatures increase, due to many factors relating toenvironmental control, there is a need for heat insulating gaskets whichcan withstand even higher temperatures.

Also, in smaller internal combusion engines, where the size of thegasket does not justify the cost involved with the type of insulatinggasket shown in said earlier patent, there is a need for a simplerconstruction which can be produced at relatively low cost.

Molded insulators have been used in the past to attempt to solve thegasketing problems in these smaller engines, but they have not beenaltogether satisfactory, due to the fact that the clamping loadsnecessary to bring the flange parts together to seal them were generallysuch that they cause the parts to crack under stress, and this conditionwas further aggravated by the fact that the flange surfaces are oftenuneven because of the expense involved in machining these parts assmooth as might be desired.

In larger internal combustion engines, such as normally found in todayshigh-powered automobile, the economics of the part are a real problem,as well as the technical problems due to the high temperature generatedin the manifold area of the engine, this often being in the range of 350to 400F, and sometimes even higher. The heat conducted from the manifoldto the carburetor through the throttle bowl joint causes a highevaporative loss of the fuel in the throttle bowl. These temperatureincreases are further hampered by the trend of design toward low profileautomobiles which provide for very cramped engine compartments, with lowhood lines. The use of sound dampening material to reduce the noiselevel in the remainder of the automobile is a further complication tothe problem because this material is heat insulating, prevents rapiddissipation of the engine heat to the ambient atmosphere, and keeps theheat of the engine at a higher level longer. Any steps which can betaken to minimize the heat buildup in the throttle bowl, and thereforeprevent vaporization of the fuel contained therein not only improve theperformance and the economy of the automobile engine, but also reducethe ecological problems with unburned petroleum fuels. The fuelevaporated may condense inside the engine compartment and drip back downonto the hot engine to be further vaporized and partially burned,causing a particulate matter to be suspended in the atmosphere.

BRIEF SUMMARY OF THE INVENTION It is an object of this invention toprovide a heat insulating gasket structure which will be particularlyeffective in extremely high temperature conditions. It is an additionalobject to provide that the insulator gasket structure may be drawn intosealing configuration without undue distortion of the gasket structureor the mating flanges of the conduit being sealed. It is also an objectto provide a gasket structure that is economical to manufacture, so thatit may be used in small engine applications, where the cost heretoforehas been a deterrent to proper gasketing techniques. It is an aim ofthis invention to provide a structure which is more resilient thanpreviously known structures so as to permit greater tolerances as far asthe flatness and alignment of the mating surfaces. It is a furtherobject to provide an air gap between the mating flanges and the gasketbody to take advantage of the great insulating value of air.

DESCRIPTION OF THE DRAWINGS j ,In the drawings:

FIG. 1 is a plan view of an embodiment of the invention;

FIG. 2 is a partial perspective view of the embodiment depicted in FIG.1; and

FIG. 3 is a sectional view along the lines 3--3 of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION Referring to the drawings wherelike numerals of reference will designate like elements throughout, andreferring specifically to FIG. 1, an improved heat insulating gasketstructure 10 is shown. The structure 10 is composed ofa molded bodyportion 12 with a fluid passageway 14 passing therethrough. Raisedbosses 16 with bolt holes 18 coaxial with the bosses are located, inthis case, at the extremities of the structure 10. Sealing members 20 ofpacking material encircle the fluid passageway 14 in the body 12. Themembers 20 are of a thickness greater than the-overall thickness of thebosses 16.

As seen generally in FIGS. 2 and 3, the gasket structure has threelevels or tiers on each mating face. The facesof the body 12 are themain planes of reference from which all other heights are determined.The bosses 16 project from the surfaces of the faces 12, and the sealingmembers 20 are affixed to the faces of the body 12 so as to encircle thefluid opening I4 at a distance greater than the projection of the bosses16. This relationship is specifically illustrated with the primedreference numerals in FIG. 3. The distance A is the thickness of themolded body portion 12 between points 12'12'. The distance B is thethickness of the raised boss portion 16 between points 16I6'. Thedistance C is the free standing thickness of the gasket structure 10taken between points I0'--I0'. The thickness of the packing or sealingmembers 20, as here shown, would be (C A )/2. Certain limitations existto make this three-tiered structure effective. The bosses must projectat least 0.005 inch above the molded body portion of the gasketstructure and may project possibly 0.030 inch above the body portion.Normally the bosses 16 would project on both sides of the gasketstructure but a particular application may necessitate bosses on oneside so that in any event the bosses will project on at least one sideof the molded body portion 12.

The height of the bosses is dependent on the gasket thickness necessaryto maintain a seal and this includes provision for the degree ofcompaction required as well as the practicability of the thicknessselected. A typical thickness of the gasket would approximate 0.020 inchwith a boss height above the molded body portion of about0.0l5 inch,keeping in mind that the total height over the bosses, including themolded body thickness,

the boss height at each side and the sealing gaskets, which may be onone or both sides, all require tolerances which must be considered inarriving at the specifications for a particular gasket structure.

The sealing members must be at least 0.002 inch above the plane of thebosses 16. Here too the member 20 normally is disposed on both sides ofthe gasket structure but always on at least one side. The width of thesealing member should normally be no more than ten times its height,with a minimum of 0.075 inch and a maximum of 0.200 inch with typicalsealing member being in the range of 0.090 to 0.200 inch. A typical bodyportion would be 0.250 inch thick, and the bossed would protrude about0.020 inch on each side of the body portion. The sealing members ofpacking material would be approximately 0.025 inch high andapproximately 0.075 inch in width encircling the fluid opening. Thesealing members would be compressed when the mating parts were drawntogether upon the raised bosses to a thickness of 0.020 inchapproximately on each side, or be approximately 20 percent compressed.The gasket with the compressed sealing member and the flanges restingupon the raised bosses is then in position with an air gap on each sideof the body portion of approximately 0.020 inch. In other cases, the airgap might be as little as 0.005 inch since the bosses 16 must be atleast 0.005 inch above the level of the molded body portion 12. This airgap serves to insulate the carburetor throttle bowl, which may be on oneside of one flange from the intake manifold, which would be on the otherside of the structure on the other flange. The insulating value of thisair gap, even when small, far exceeds any detrimental conductivitythrough the bossed portions of the body of the gasket.

While the factor of these bossed portions may be higher than would besuitable for the entire gasket, the fact that the area in contact withthe flanges is as minimal as it is, as well as the fact that the area ofthe packing material of the sealing member is minimal compared to theplan area of the flanges being sealed, provide for a very goodinsulation of the joint sealed.

The materials used in making the body portion of the insulating gasketstructure of this invention will generally be moldable materials such asasbestos phenolic molding compounds. These materials are phenolic resinsto which asbestos fibers have been added to give additional strength andresilience. Typical of the commercially available compounds that havebeen found useful for making the body portion are Gene] 4300 from theGeneral Electric Co. and No. 25398 from Reichhold Chemical. The moldswill ordinarily be such that the cavity provides that the bossesprotrude the same distance above and below the faces of the bodyportion. Other materials and molding techniques known to the art may beused.

The sealing members will be compactible and compressible packingmaterials. The specific material is selected for its compatibility withthe environment of use. Factors of prime importance are temperatureranges, corrosiveness of fluid, and clamping pressure. The packingmaterials known in the art, such as curable nitrile rubber,acrylonitrile rubber, neoprenes, and chloroprenes may be suitable. Iprefer asbestos rubber sheet packing, such as Kaobestos 66013, sold bythe F. D. Farnam Co., for the reasons that it provides good sealing of awide range of fluids over a broad temperature range, and the material isvery stable at the high temperatures which are contemplated in the fieldof use.

A typical heat insulating gasket structure may be assembled as follows:A sheet of Kaobestos 66013 is coated on one side with an elastomeradhesive resin, such as Farnam l800l-XR, and dried. This adhesive, whichis particularly suitable for the gasket structure environment, is awater dispersion of curable neoprene and a phenolic resin emulsion ofthe type disclosed in Farnam et al. US. Pat. No. 3,158,526. The sealingelements 20 are then die-cut to the desired configuration. The die-cutpieces are then put into an auto feed device to be indexed upon thepreheated faces of the molded body portion. The molded body portion ispreheated to about 200F., and the dried adhesive coated faces of thesealing elements become tacky upon contact with the preheated insulator.These elements are pressed over a dwell time of one to five seconds. Thebond lines of the structures are cured in an oven over a period of 10 to15 minutes at temperatures of about 325 to 350F. The finished parts areremoved to cool, and then will be inspected and packaged.

The size, shape and assembly conditions have a hearing on the selectionof the flange width, which may be of uniform width over the entire areaor the width may be variable. The primary purpose of the inventionincludes the provision of a minimum gasket area under clamp load,thereby increasing unit loading and minimizing distortion, or bending ofthe mounting flanges, while gaining an insulating air gap and keepingthe width of the sealing member at a minimum.

The embodiments in which an exclusive property or privelege is claimedare defined as follows:

1. A heat insulating gasket for use between mating flanges of aninternal combustion engine conduit or the like, said gasket comprising aunitary molded core member of insulating material having a body portionof given thickness, having bolt holes and a fluid passagewaytherethrough, bosses coaxial with said bolt holes projecting from thesurfaces of said body portion to a greater thickness than the. thicknessof said body portion, die-cut sheet packing material on said bodyportion of said core surrounding said fluid passageway projectingfurther from said body portion than said bosses project, the total planarea of said packing material being less than 33 /3 percent of the planarea of the core member, whereby when the gasket structure is clampedbetween said mating flanges, said packing material will be compressed tothe level of said bosses forming a seal between said flanges andsubstantial air spaces will be provided between said flanges and saidcore member for heat insulating purposes.

2. The heat insulating gasket structure as set forth in claim 1 whereinthe said packing material projects at least 0.002 inch further from saidcore member on each side than do said bosses.

3. The heat insulating gasket structure as set forth in claim 1 whereinsaid air spaces will be at least 0.005 inch thick.

4. A heat insulating gasket structure for use between mating flanges ofan internal combustion engine conduit, said gasket comprising a unitarycore of insulating material having a body portion of given thickness,having a fluid passageway and bolt holes, raised bosses coaxial withsaid bolt holes projecting at least 0.005 inch from the surfaces of thebody portion, die-cut sheet packing material mounted on said bodyportion of said 6 said mating flanges, said packing material will becompressed to the level of said bosses thereby forming a seal betweensaid flanges and substantial air spaces will be provided between saidflanges and said core member for heat insulating purposes.

1. A heat insulating gasket for use between mating flanges of aninternal combustion engine conduit or the like, said gasket comprising aunitary molded core member of insulating material having a body portionof given thickness, having bolt holes and a fluid passagewaytherethrough, bosses coaxial with said bolt holes projecting from thesurfaces of said body portion to a greater thickness than the thicknessof said body portion, diecut sheet packing material on said body portionof said core surrounding said fluid passageway projecting further fromsaid body portion than said bosses project, the total plan area of saidpacking material being less than 33 1/3 percent of the plan area of thecore member, whereby when the gasket structure is clamped between saidmating flanges, said packing material will be compressed to the level ofsaid bosses forming a seal between said flanges and substantial airspaces will be provided between said flanges and said core member forheat insulating purposes.
 2. The heat insulating gasket structure as setforth in claim 1 wherein the said packing material projects at least0.002 inch further from said core member on each side than do saidbosses.
 3. The heat insulating gasket structure as set forth in claim 1wherein said air spaces will be at least 0.005 inch thick.
 4. A heatinsulating gasket structure for use between mating flanges of aninternal combustion engine conduit, said gasket comprising a unitarycore of insulating material having a body portion of given thickness,having a fluid passageway and bolt holes, raised bosses coaxial withsaid bolt holes projecting at least 0.005 inch from the surfaces of thebody portion, die-cut sheet packing material mounted on said bodyportion of said core surrounding said fluid passageway projecting atleast 0.002 inch further from said body portion on each side than saidbosses project, the width of said packing material being no more thanten times its thickness, the total plan area of said packing materialbeing no more than 33 1/3 percent of the plan area of said core member,whereby when the gasket structure is clamped between said matingflanges, said packing material will be compressed to the level of saidbosses thereby forming a seal between said flanges and substantial airspaces will be provided between said flanges and said core member forheat insulating purposes.